The present invention relates generally to an optical system, and more particularly an objective optical system well fit for all sky cameras or the like adapted to form hemispherical object images on a zonal-form flat image plane and a projection optical system suitable for use with panoramic projectors or the like adapted to project zonal images located on an image plane onto a hemispherically curved surface.
In methods heretofore, when projecting images projected onto a domed screen, a plurality of images projected independently through a plurality of projectors have been put together or projected through a wide-angle optical system such as a fisheye lens.
For instance, Japanese Patent Application Publication No. 2001174713 shows an objective optical system for endoscope applications, in which the first reflecting surface that is rotationally symmetric about the center axis and includes an annular convex surface, and the second reflecting surface including a convex surface, are located in front of an image-formation lens to form a hemispherically curved object on a plane. However, there is nothing specific set forth about the optical system whatsoever.
Further, Japanese Patent Application Publication No. 2004287435 shows that a beam splitter, a concave mirror and a ball lens array are combined together to convert a flat image into a curved image.